The present invention relates to an actuator for moving a tool, the actuator comprising a housing on which is provided an axially movable tappet with a cutting tool holder, the tappet being moved using a rapid drive, preferably a piezoelectric transducer, which is biased against a restoring force and is, preferably, dampened by a damping element.
The invention further relates to a device for machining work pieces using such an actuator.
An actuator and a device of that kind are known from DE 20 2004 011 815 U1.
The known actuator is used in a lathe for producing very finely structured surfaces of rotationally symmetric or, especially, rotationally non-symmetric configuration.
To this end, the lathe comprises a spindle, which can be driven to rotate about its longitudinal axis and which carries a fixture for chucking a work piece, with an actuator provided with a rapid drive, for example in the form of a piezoelectric drive, for producing a rapid movement of the tool in a direction substantially perpendicular to the surface of the tool, while a second drive that produces a linear feed motion in the first direction allows the actuator to be positioned along a work piece surface to be machined. The rapid drive of the actuator is coupled with the tool via guide means that allow the tool to be fed in the axial direction of the rapid drive, against a restoring force, while exhibiting high rigidity in a plane perpendicular to that direction. The actuator comprises a sintered plate, permeable to air, which acts as a damping element via an enclosed air volume with a view to reducing the effects of cutting force noise in operation of the actuator.
It has been found in operation that such an actuator permits microstructured surfaces to be produced even when hard materials, such as steel or other materials are to be machined.
Another actuator of a similar kind, and a device for machining work pieces using an actuator, are known from the thesis by Robert Hilbing entitled “Genauig-keitssteigerung von Präzisionsdrehmaschinen durch aktive Kompensation dynamischer Störungen (Increasing the accuracy of precision lathes by active compensation of dynamic noise)”, RWTH Aachen (Shaker Verlag, vol. 16/2004, D82 Diss. RWTH Aachen).
The actuator is used in combination with a lathe for producing high-quality rotationally symmetric surfaces. The actuator comprises a piezoelectric drive, which while being movably guided in the axial direction via a double-diaphragm spring, exhibits high rigidity in a direction perpendicular to that direction. A tool holding fixture is mounted on a tappet that encloses a piezoelectric drive, being directly connected with the latter. The piezoelectric drive in its turn is bonded to a base plate which is biased against the piezoelectric drive by a set of springs. A radial bearing is formed by two mutually spaced diaphragm springs on which the tappet is suspended.
A damping system is not provided in the case of that actuator. Further, the production of finely structured surfaces would require active electric compensation of dynamic noise which, due to the natural frequency of the spring mass of the actuator, that is to be suppressed, and due to the comparatively long transfer time between the sensor and the actuator, can be realized only at high expense, if at all. While the known arrangement is suited for machining non-ferrous metals, it is not suited for machining hard materials, such as steel.